Crossmodal plasticity of sensory cortical processing

Sensory systems do not work in isolation. Moreover, it is well known that visual deprivation (such as blindness) can lead to improved auditory abilities. However the underlying mechanisms that contribute to these “supernormal” abilities are largely unknown. For example it could be that neurons in the visual cortex are recruited to subserve auditory processing, or that neurons in the auditory cortex become better in processing sounds, or some combination of these two mechanisms. Many studies have investigated changes in the visual cortex in long-term blindness and found crossmodal activation of the visually deprived visual cortex (for example by braille reading). We are interested in investigating what happens to other cortical areas in particular the auditory cortex when visual experience is altered for just a short period at older ages. We are looking at how auditory processing and micro-circuits are altered. Our results so far show that brief visual deprivations (simulated blindness) alter auditory processing in that neurons have better frequency discrimination  abilities and lower thresholds. Moreover we find that thalamocortical synapses in auditory cortex are strengthened (Petrus et al Neuron 2014, see F1000 review, BBC, NPR, Washington Post, Nature.com, Voice of America). Besides thalamocortical strengthen we also observe a profound refinement and strengthening of intracortical connections (Meng et al. Cell Reports 2015, Petrus et al. 2015) which can underlie the sharpening of receptive fields.

 
Thus some of the changes seen in auditory performance are likely due to changes in the auditory cortex. Seeing changes in thalamocortical connections is quite surprising as our visual deprivations occur after the critical period and indicate that crossmodal influence seem to be more powerful than unimodal influences in changing cortical circuits.  These results raise the question how the lack of vision is signaled to the auditory cortex and how one would might make such changes permanent.
 
We are collaborating in this project closely with the lab of Dr. Hey-Kyoung Lee at Johns Hopkins University.
 
Patrick Kanold
Department of Biology